Mike PleziaInside service technician, Clark Associates · Commercial Equipment, HVAC, and Refrigeration professional

Reading a Wiring Diagram with Your Meter

18 Sept 2026 · 2 min

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1:41

In this instructional segment, the presenter walks beginners through the process of testing motor capacitors using a multimeter. He explains the role of capacitors in single‑phase motors, distinguishes start and run capacitors, and emphasizes safety by requiring power to be shut off at the breaker and disconnect and by discharging the capacitor with an insulated screwdriver across each terminal pair. He then shows how to set the meter to the microfarad (µF) setting, measure the capacitance, and compare the reading to the label rating, applying a ±6% tolerance rule. An "OL" (over‑limit) reading indicates a dead capacitor that must be replaced. The guide aims to equip DIYers and tradespeople with a clear, step‑by‑step method for safely diagnosing capacitor health.

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Hey, are you new to the trades? Here's something you may not know about testing capacitors with your meter. Look for the symbol that looks like 2 parallel lines labeled microfarads. Here's what a capacitor actually does: it stores a charge and releases it to help a motor start and keep spinning. Without it, a single-phase motor can't get the torque it needs on its own. You'll run into 2 types: A start capacitor kicks in only for a moment, then drops out. A run capacitor stays in the circuit the whole time the motor's operating, often a dual run cap with terminals for common, the compressor, and the fan. Now, before you touch this thing, discharge it first. Always power off at the breaker and the disconnect, both. Insulated screwdriver, By the handle. Only. Touch the shaft across each pair of terminals. A little pop is normal. Do this across every terminal combination, not just one. Only then is it safe to test. Set your meter to microfarads. Touch your probes across the terminals. Let the number settle. Now compare it to the rating printed on the label. There's a tolerance here— the 6% rule. Reading needs to fall within 6% of the rated number, above or below. Outside that range? It's weak. Time to replace it. See OL on the display? It's dead, no question. Now that you know, you can help someone else know.